Modern vehicles are increasingly equipped with electrically operated parking brakes which are also referred to as automatic parking brakes (APB). Systems of this type usually include an operating element, e.g., a push-button, using which the parking brake may be locked and/or released. A control unit, which is connected to the operating element, recognizes the intention of using the parking brake and activates an actuator accordingly, such as a hydraulic pump or an electric motor, to lock or release the parking brake.
For this purpose, known parking brakes include a mechanical locking device which locks the brake calipers in the engaged position. The locking device is usually also operated by hydraulic or pneumatic pressure or is motor-driven. The respective elements, e.g., a hydraulic pump or an electric motor, are accordingly activated by a control unit.
Automatic parking brakes offer increased comfort and safety to the driver, since they are operatable simply by pushing a button. As soon as the parking brake has been successfully locked, the proper state of the parking brake is displayed to the driver with the aid of a function lamp. The lighting up of the function lamp does, however, not mean that the parking brake is in fact capable of holding the vehicle. Under unfavorable circumstances, e.g., when the vehicle is parked at a great downhill grade or when the brake disks are very hot, the clamping force of the parking brake may not be sufficient to reliably hold the vehicle. In the worst case, the vehicle is at risk of starting to roll.